Utilities to save disk space

 GNU cp used to detect files that contain 0-filled holes and save disk space
 by skipping them with lseek when writing a file and thus not allocating
 disk blocks. Unfortunately it does no longer. So here is program to make
 holes in existing files.
 .
 Also there are some scripts that help cleaning up the hard disk
 (finding duplicated and/or unstripped files).